To make this Eggnog Snickerdoodles Recipe gluten free, replace the all-purpose flour with a certified gluten-free 1:1 baking flour blend. Verify that the cream of tartar, baking soda, spices, vanilla extract, rum extract, powdered sugar, eggnog, and all packaged ingredients are labeled gluten free or free from gluten-containing additives. Use clean mixing bowls, measuring cups, utensils, baking sheets, and parchment paper to prevent cross-contact with gluten-containing ingredients.